1. Field of the Invention
Methods and apparatuses consistent with the present invention relate to restoring content, and more particularly, an aspect of the invention relates to a method and apparatus for effectively fixing up a transform part of content.
2. Description of the Related Art
The standard for the AACS (Advanced Access Content System), which is a next-generation optical disc protection system, uses a broadcast encryption scheme that does not allow a player having a device key set revoked due to hacking and so on to decrypt content encrypted according to the broadcast encryption scheme. In the broadcast encryption scheme, a different device key set is allocated to each player, and an intermediate key encrypted using a revoked device key set is not stored in discs that are distributed to the public, thereby preventing a player having the revoked device key set from acquiring the intermediate key. Thus, the player having the revoked device key set cannot obtain a content decryption key.
However, even if a device key set is not disclosed, hacking software may be created based on structural flaws of a specific player model. In this case, a large number of players may be hacked by the hacking software, and thus, it is impossible to revoke all device key sets allocated to the hacked players in order to cope with this situation.
To solve this problem, an individual content renewability scheme has been introduced to control restoration of content by using programmable code for each content. In the renewability scheme, security code controlling restoration of content is stored in a disc. The security code is executed before reproduction of the content so as to determine whether there are problems in reproducing the content. For instance, it is determined whether a device key set of the player has been disclosed or whether hacking software is installed or is running. Then, the content is restored only when it is determined that there is no problem in the content reproduction process. In other words, it is difficult to upgrade an already sold player, but a disc can be upgraded at a content level by storing the security code thereon.
FIG. 1 is a block diagram of a conventional media player 1. Referring to FIG. 1, the conventional media player 1 includes a media interface 11, a virtual machine 12, a memory 13, a decrypting/decoding unit 14, and an output interface 15.
The media interface 11 reads content and security code, which is a program protecting the content, from a medium, such as a digital video disk (DVD) and a compact disk (CD).
The virtual machine 12 executes the security code read by the media interface 11 to generate information of the media player 1, and compares the generated information with information of the media player 1 which has been stored in the memory 13. Next, the virtual machine 12 determines whether a device key set of the media player 1 has been disclosed or hacking software thereof is installed or is running based on the comparison result, and further executes the security code to generate information for controlling content restoration only when it is determined that the device key set of the media player 1 has not been disclosed or the hacking software thereof is not installed or is not running.
The decrypting/decoding unit 14 decrypts and decodes the content, which is read by the media interface 11, by using the information generated by the virtual machine 12. If the content is encrypted according to content protection standards, such as the CSS standards or the AACS standards, the decrypting/decoding unit 14 decrypts the content read by the media interface 11 according to the content protection standards used to encrypt the content. If the content is coded according to the MPEG-2 standards, the content is decoded according to the MPEG-2 standards.
The output interface 15 outputs the content, which was decrypted and decoded by the decrypting/decoding unit 14, to a display device, such as a digital Television (DTV).
As described above, a conventional, individual content renewability scheme provides a solution to control content restoration according to whether a device key set of a media player has been disclosed or whether a security environment for the media player is normal. However, the conventional, individual content renewability scheme does not provide a solution to protect content against frequent attacks of a hacker throughout content reproduction, for example.